Passive infrared sensing devices have become commonly used for sensing intruders in various types of protection systems as well as for detecting the approach of customers or residents for the purpose of opening doors or turning lights on. In many instances, it is both desirable and important to detect sources of incident radiation throughout a region.
Regional detection can readily be accomplished by using multiple sensors. However, this can become expensive.
It would be desirable to be able to sense a source of radiant energy using a single sensing apparatus with a field of view on the order 180.degree.. Further, it would be desirable to be able to do this using a relatively minimum number of lenses or reflectors/deflectors. It is also desirable to be able to do this with inexpensive optics so as to reduce the total price of the product.